A sculptor has 12 blocks of marble. He carves one block in 5 hours. After 4 blocks, he injures his wrist and slows by 50%. Total time to finish?

Explanation

To solve this problem, break it into two parts. For the first 4 blocks, the sculptor takes 4 blocks * 5 hours/block = 20 hours. After the injury, his speed is halved, meaning he now takes 5 hours * 2 = 10 hours per block. However, this is an incorrect interpretation. Instead, if his speed is halved, the time per block is doubled: 5 hours * 2 = 10 hours per block, totaling 8 blocks * 10 hours/block = 80 hours. This would be incorrect, as the correct slowdown factor should be applied to the block time, resulting in 8 blocks at 10 hours/block, but this is a miscalculation. The correct approach is 8 blocks at 5 hours/block * 2 = 40 hours, but with the initial error, the calculation shows 55 hours. The correct total should be 20 hours + 55 hours = 75 hours. Therefore, the correct answer is 75 hours.